Mayan spawn date is pretty bad for Iroquois, true.... Perhaps I could use the Vikings instead (another easy 'Minor civ' change.) But if I have to change the DLL for the spawn date (I would use 900 or so AD for the Iroquois, because I want to give them a chance to achieve their first UHV, 'Be the first to Constitution'.) can I also change the number of Civs, thus making any civ-removal redundant?
Changing the setup of Civs, period, is hard with RFC. This includes changing the number of Civs and removing any...
Once I have read and comprehended your excellent textbook link (it's going great!) should I have the minimum Python knowledge to mod the UHV/UP?
Great! That book (How to Think Like a Computer Scientist) will pretty much teach you the works. (I never even read the last two chapters, as I thought is was going into peripheral territory.) Sure, there is always more stuff to learn but you will know about every aspect there is to Python programming. Unfortunately the book won't teach you about Civ modding as such, but I can teach you the basics once you know Python.
If you get through the book you will pretty much be equipped to redesign all the Python in RFC. I don't even think Rhye knew half of what that book can teach you when RFC was originally made... (Not to be disrespectful, but I get that from looking at the actual code. So you don't necessarily have to do things the way Rhye did - do what the book tells you to instead.)
The real test of your progress comes later in the book - there is card game simulator (Old Maid Hand) used as an example for learning something called Object-Oriented Programming. I thought it was very hard to follow the whole thing, but once I did manage to understand every aspect of the code (I got help

), then I knew how to do the really advanced stuff with Python. Also, I realized that CivIV Python uses Object-Oriented Programming, so the book was actually
really helpful!
So be prepared to tackle that hurdle once it comes along. I think I have the entire script for the example game if you need to look at it. (The example code is spread out over several chapters, which doesn't make it easier to follow.)
And one more thing. Does PyScenario help with spawn triggers? If I wanted the Iroquois to spawn in 960 AD, would PyScenario help? or would I need to go into the DLL anyway?
You mean changing the spawn date? No, this has to be done both in Consts.py and in the SDK. The hard part isn't supposedly to change the date itself, but rather to recompile the DLL. Unfortunately I wouldn't even know where to start...
PyScenario is just a tool to help non-programmers spawn units and cities and whatnot, or to change map tiles, flip cities, grant Techs or the like. If you learn actual Python there is nothing PyScenario can do that you cannot do on your own (minus all the limitations). You can take a look at the
CivIV Python API to whet your appetite...